Blade outer air seal with machinable coating at sealing surfaces

Abstract

A gas turbine engine includes a compressor section, a combustor section and a turbine section for rotation on an axis. The turbine section includes at least one row of rotating turbine blades each having a radially outer tip. A blade outer air seal is positioned radially outwardly of the radially outer tip. The blade outer air seal has a central web positioned radially outwardly of the radially outer tip. The blade outer air seal has an upstream mount arm and a downstream mount arm receiving mount structure from a static structure. The static structure has sealing members engaging an upstream outer surface of the upstream mount arm at an upstream seal material and a downstream outer surface of the downstream mount arm at a downstream seal material. A method is also disclosed.

What is claimed is: 
     
       1. A gas turbine engine comprising:
 a compressor section; 
 a combustor section; and 
 a turbine section for rotation on an axis, the turbine section including at least one row of rotating turbine blades each having a radially outer tip; and 
 a blade outer air seal positioned radially outwardly of the radially outer tip, the blade outer air seal formed of ceramic matrix composite materials, the blade outer air seal having a central web positioned radially outwardly of the radially outer tip; 
 the blade outer air seal having an upstream mount arm and a downstream mount arm mounted to a static structure, the static structure having respective sealing members each engaging a respective upstream outer surface of the upstream mount arm at an upstream seal material and a respective downstream outer surface of the downstream mount arm at a downstream seal material, at least one of the upstream seal material and the downstream seal material being formed of a bond layer deposited on the mount arm, and a seal layer deposited on the bond layer; 
 a seal thickness in an axial direction defined for the combination of the bond layer and the seal layer at a contact location with a respective one of the sealing members; and 
 a mount arm width of a respective one of the upstream mount arm and downstream mount arm associated with the at least one of the upstream seal material and downstream seal material has a width at a radial location of the contact location and a ratio of the seal thickness to the mount arm width is greater than or equal to 0.4 and less than or equal to 0.8. 
 
     
     
       2. The gas turbine engine set forth in  claim 1 , wherein said bond layer and seal layer are formed at both the upstream seal material and the downstream seal material. 
     
     
       3. The gas turbine engine as set forth in  claim 2 , wherein the bond layer is formed of silicone. 
     
     
       4. The gas turbine engine as set forth in  claim 3 , wherein the seal layer is formed of one of rare earth silicates, alkaline earth silicates, alkaline earth aluminosilicates, yttria-stabilized zirconia, alumina-stabilized zirconia, mullite, titania, chromia, silicon, silicon oxides, silicon carbides, silicon oxycarbides, barium-magnesium aluminosilicate, hafnium oxides including hafnon, hafnium silicon oxides, alumina-stabilized zirconia, zirconium oxides including zircon, yttrium oxides including yttria, mullite, and combinations thereof. 
     
     
       5. The gas turbine engine as set forth in  claim 4 , wherein the seal layer is formed of mullite. 
     
     
       6. The gas turbine engine as set forth in  claim 5 , wherein the sealing member contacting the upstream seal material has a spring bias away from the static structure. 
     
     
       7. The gas turbine engine as set forth in  claim 6 , wherein the upstream seal material and downstream seal material are formed in part on said respective ones of the upstream and downstream mount arms, and also extending to a radially outer side of the central web. 
     
     
       8. The gas turbine engine as set forth in  claim 5 , wherein the upstream seal material and downstream seal material are formed in part on said respective ones of the upstream and downstream mount arms, and also extending to a radially outer side of the central web. 
     
     
       9. The gas turbine engine as set forth in  claim 8 , wherein an axial thickness of the bond layer in each of the upstream seal material and downstream seal material being less than an axial thickness of the seal layer. 
     
     
       10. The gas turbine engine as set forth in  claim 1 , wherein the seal layer is formed of mullite. 
     
     
       11. The gas turbine engine as set forth in  claim 10 , wherein the sealing member contacting the upstream seal material has a spring bias away from the static structure. 
     
     
       12. The gas turbine engine as set forth in  claim 11 , wherein the upstream seal material and downstream seal material are formed in part on said respective ones of the upstream and downstream mount arms, and also extending to a radially outer side of the central web. 
     
     
       13. The gas turbine engine as set forth in  claim 12 , wherein an axial thickness of the bond layer on the at least one of the upstream seal material and downstream seal material being less than an axial thickness of the seal layer. 
     
     
       14. The gas turbine engine as set forth in  claim 10 , wherein an axial thickness of the bond layer on the at least one of the upstream seal material and downstream seal material being less than an axial thickness of the seal layer. 
     
     
       15. The gas turbine engine as set forth in  claim 1 , wherein the sealing member contacting the upstream seal material has a spring bias away from the static structure. 
     
     
       16. The gas turbine engine as set forth in  claim 15 , wherein the upstream seal material and downstream seal material are formed in part on said respective ones of the upstream and downstream mount arms, and also extending to a radially outer side of the central web. 
     
     
       17. The gas turbine engine as set forth in  claim 1 , wherein the upstream seal material and downstream seal material are formed in part on said respective ones of the upstream and downstream mount arms, and also extending to a radially outer side of the central web. 
     
     
       18. The gas turbine engine as set forth in  claim 1 , wherein an axial thickness of the bond layer on the at least one of the upstream seal material and downstream seal material being less than an axial thickness of the seal layer.